Drought is never easy for wildlife, and even less so for people and domestic stock. While dry cycles are part of the natural process, there is a growing awareness of climate change and human impact on our water resources.
According to the South African Weather Service, iSimangaliso has received below-average summer rainfall and is experiencing extremely dry conditions. Rainfall for July to October 2014 was in the region of 100-200mm compared with 200-300mm for the same period in 2013. Consequently, water levels in the lakes, rivers, wetlands and pans across iSimangaliso are very low.
Lake St Lucia is a 36,000ha system with fluctuating depths and varying salinities. Although not unexpected, water levels in Lake St Lucia dropped through the winter of 2014 to just above mean sea level. With little summer rainfall, levels have dropped further and the water body has shrunk, while salinity levels have risen in the northern sections of Lake St Lucia to about 50 parts per thousand (ppt) at Lister’s Point and the Nhlozi Peninsula. Typically seawater ranges between 30–35 parts per thousand (ppt). The driver of the natural variability in depth and salinity is the seasonal variation in rainfall.
Droughts are a natural part of the weather patterns in iSimangaliso and drive biodiversity and resilience. It is this biodiversity that contributed to iSimangaliso’s listing as South Africa’s first World Heritage Site.
“Lake St Lucia is in a better state than during the previous drought, which spanned eight years from 2002 to 2010 when there were extremely low water levels, desiccation of large areas of the lake, and extreme hypersalinity. During the last drought I vividly recall walking across the lake from Catalina Bay to Charters Creek without getting my feet wet,” says Andrew Zaloumis, iSimangaliso CEO. “If we do not get good rains this summer and uMfolozi River water into the system, conditions could well become dire.”
Estuarine scientist Nicolette Forbes says that, “The fact that Lake St Lucia is in better shape during this drought is largely due to iSimangaliso’s mouth management strategy, which has allowed the uMfolozi River to follow its natural path into Lake St Lucia since 2012. This resulted in increased water levels and initiated the process of restoring estuarine functioning and a normal salinity range over the past 24 months. The uMfolozi is Lake St Lucia’s largest catchment and is the main freshwater source (about 60%) to this estuarine system. Its importance increases during dry years. In addition, the substantial land restoration of the Eastern and Western Shores has also assisted and contributed to the water balance needs of the estuary.”
The 2015 winter waterbird counts provide a good indication of the ecological condition of Lake St Lucia. As a Ramsar Wetland of international importance and UNESCO world heritage site, these counts are important in assisting management to keep its finger on the pulse of the overall condition of the system.
The aerial survey completed on the 9th June counted over 16,500 waterbirds across the lake. The dry condition suits both the approximately 4,200 greater flamingos as they stand in shallow water when feeding, and the greater white pelicans (approximately 4,100). There are also currently over 950 Caspian terns with about 300 active Caspian tern nests.
As one of Africa’s best game viewing hides, kuMasinga Hide in iSimangaliso’s uMkhuze section is supplied with pumped water to assist in times of low rainfall. The wildlife and bird sightings are incredible here and a huge attraction for tourists.
From a game perspective, pans and water points on the Eastern Shores, Western Shores and uMkhuze are very low or dry. A system of boreholes and water supply points for animals is in place across the park. As part of our drought preparation, these have all been serviced and operationally tested. Auxiliary water systems such as uBhejane Pan on the Western Shores, kuMasinga Hide at uMkhuze and Mfazana Pan on the Eastern Shores have been switched on, resulting in some spectacular game viewing and birding. The situation is being closely monitored and other pumps will be switched on as and when necessary. Further maintenance to the water supply system is underway.
Lake Sibaya is South Africa’s largest coastal freshwater lake with a historical estuarine past. It is fed almost entirely by groundwater seepage, and levels constantly fluctuate in response to varying amounts of groundwater discharge into the lake, seepage loss through the coastal dunes, abstraction and evaporation from the lake surface. Levels are very sensitive to local weather conditions and show direct responses to local rainfall conditions and seasonal cycles. Unsurprisingly the levels are, therefore, low at the moment and this has accentuated the two sand spits, which are in the process of growing towards one another from the opposite banks. Data from previous studies show that these are rapidly growing features with high sedimentation rates, which may result in permanent lake segmentation in the long-term.
It is also likely that the rates of water abstraction from the lake for human consumption, combined with decreasing rainfall and rapidly increasing commercial plantations, may have exacerbated the observed decreases in lake level. By volume, the current abstractions have been evaluated as “small” relative to the large volumes flowing in and out of the lake. However, water level records show a different story and indicate that the lake may be more vulnerable to abstraction and adjacent stream flow reduction from tree plantations. An iSimangaliso commissioned study is currently underway to look at the interactions between groundwater levels and lake water levels in response to different water uses.
What has been done to counter the effects of the drought?
“Droughts are part of the natural cycle and management of the World Heritage Site. The restoration and rehabilitation work undertaken in iSimangaliso has gone a long way to improving the resilience of the park to extreme weather patterns”, says Zaloumis. “However, in the medium to long-term managers will increasingly need to develop responses to the conditions that are emerging as a result of changing weather patterns and global warming.”
In the last fourteen years, significant progress has been made in the restoration of degraded habitats. iSimangaliso has effected the removal of over 24,000ha of exotic commercial timber plantations on Lake St Lucia’s Eastern and Western Shores and implements major community-based, labour intensive land care programmes with the Department of Environmental Affairs, which include Working for Water, Working for Wetlands and Working for Fire, across iSimangaliso. This has provided an important support function to the lake system and improved its resilience to natural salinity fluctuations.
Progress has also been made in the hydrological restoration of the Lake St Lucia estuarine system by iSimangaliso with funding from the Global Environment Facility. Based on the most recent scientific work undertaken, the uMfolozi River is being allowed to reconnect with Lake St Lucia, and an active monitoring programme has been put in place.
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